One week after Ukrainian industrialist Dmitri Firtash was arrested in Europe on Chicago corruption charges, Firtash has made bond. But the mystery continues: what is he accused of doing in Chicago?

The 48-year-old business tycoon posted $174 million in bail money, said to be a record in Vienna where he was being held, and Firtash was ordered to remain in Austria and not return to his Ukranian home. The hope is that will prevent him from fleeing to Russia where he has deep business and, some say, organized crime connections, and where extradition to Chicago would be difficult. And Friday night the Chicago case was still cloaked in secrecy.

Federal authorities in Chicago say the FBI has been on this investigation since 2006. But the us attorney's office that now has criminal charges against Dimitri Firtash will not disclose what the specific charges are or any other details about the case. Firtash, whose billionaire status from Russian natural gas took a hit recently, was arrested on a Chicago warrant last week. He was held here in Vienna until Friday, when he made bond.

In the first extensive statement since being arrested, this Ukrainian oligarch said his Chicago arrest warrant "was without foundation, and I believe strongly that the motivation was purely political."

In Chicago, U.S. Attorney Zachary Fardon has said the arrest had nothing to do with the current political and military clash between Russia and the Ukraine.

But Firtash says, "The future of Ukraine is at a delicate and defining point. I have worked behind the scenes for many months with a variety of political and religious leaders to try and help my nation. As the largest private sector employer in Crimea, my absence from Ukraine, I believe, will further destabilise (sic) a political process that involves many people working around the clock to achieve peace."

It is not clear, and authorities have not said, which of his business interests resulted in the Chicago corruption investigation. The I-Team has found no apparent commercial or personal connections that Firtash has in Chicago.

A diplomatic cable from the U.S. ambassador in Ukraine published by Wikileaks has reported that Firtash was connected to this man, Russian mob boss Seymon Mogilevich, who is currently one of the FBI's most wanted and dangerous fugitives.

According to the Wikileaks cable, Firtash acknowledged ties to the Russian organized crime figure, stating that he needed Mogilevich's approval to get into business in the first place.

Since that 2008 cable from the U.S. ambassador, Firtash has denied having mob ties.

As for the mystery of the Chicago charges, we've learned more about what Firtash faces here from Austrian law enforcement officials, who say he is suspected of bribery and forming a criminal organization in the course of foreign business deals.